Cooking stove

ABSTRACT

This invention relates to cooking stoves, in particular, to lightweight, efficient, and portable outdoor cooking stoves for use primarily by those undertaking general camping or other outdoor leisure pursuits, or by larger groups of people for entertaining or humanitarian purposes. The cooking stoves are designed to make efficient use of solid fuel blocks and to minimise the soot deposited on the cooking vessel.

FIELD OF THE INVENTION

This invention relates to cooking stoves, in particular, to lightweight,efficient, and portable outdoor cooking stoves for use primarily bythose undertaking general camping or other outdoor leisure pursuits, orby larger groups of people for entertaining or humanitarian purposes.The cooking stoves are designed to make efficient use of solid fuelblocks and to minimise the soot deposited on the cooking vessel.

BACKGROUND TO THE INVENTION

Outdoor enthusiasts and military personnel that carry their ownequipment, often for extended periods of time, need their equipment tobe lightweight and suitable for compact storage. Environments that donot offer a source of fuel, such as dried wood, are frequentlyencountered, requiring the prudent person also to carry their own fuel.Stoves that can be used with solid fuel blocks have been developed. Inaddition to their use by outdoor enthusiasts and military personnel,solid fuel blocks are well suited to humanitarian applications.

Solid fuel blocks that are on the market include hexamine blocks,trioxane blocks, solidified methyl decanoate blocks and gelled alcoholpacks. These blocks prevent the need for extra containers (as with gasor liquid fuels) or regulation equipment (pressure regulators or valves)and reduce the risk of fuel spillage or other accidental release.

Methyl, ethyl, propyl, or butyl esters of a C6-C14 carboxylic acid, ofwhich methyl decanoate is the most popular, are particularlyadvantageous as the fuel of solid fuel blocks. The C8-C14 methyl estershave favourable flash points and boiling ranges for solid fuel blocks.The present invention concerns stoves designed to be used with theseparticular fuels.

Prior art stoves have generally not been designed specifically withburning solid fuel blocks in mind. Instead, most prior art stoves havebeen designed to utilise a number of fuels, including wood. Theefficiency with which these stoves transfer heat from burning solid fuelblocks to a cooking vessel is not optimal.

When using a solid fuel block, the fuel block is placed in thecombustion chamber of the stove and a cooking vessel is placed on top ofthe stove. The solid fuel is set alight and the flames heat the cookingvessel. A problem that is typically encountered with solid fuel blocksis that fuel blocks burn aggressively leading to tall flames. These tallflames often spill out of the top of the combustion chamber and spreadout around the sides of the cooking vessel, resulting in lost heatenergy. This lost heat energy must be accounted for by burningadditional fuel blocks. In the long term this has environmentalimplications and in the short term means that a greater number of fuelblocks must be carried by the operator.

Further, if prior art stoves are used with solid fuel blocks, the fuelfrom the fuel blocks often does not completely combust, which leads todangerous volatile organic compounds (white smoke) and/or soot (blacksmoke) being produced. The volatile organic compounds and/or soot aredeposited on the cooking vessel, which makes it dirty to handle andstore, and is unhygienic.

There is, therefore, a need to provide a stove that can burn solid fuelblocks more efficiently and reduce the soot deposited on the cookingvessel. The present invention aims to meet this need.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention relates to a cookingstove, the cooking stove comprising walls which define a base at one endand a top at the other end, wherein the walls of the cooking stoveadditionally define:

-   -   a fuel zone which is defined by the section of the walls which        extends up from the base to about one third of the height of the        stove;    -   an exhaust zone which is defined by the section of the walls        which extends down from the top by about one third of the height        of the stove; and    -   a combustion zone which is defined by the section of the walls        which extends from the fuel zone to the exhaust zone; wherein        the cooking stove is characterised in that    -   the fuel zone has at least one air inlet, wherein the total        surface area of this air inlet or air inlets is 0.5% to 2.5% of        the total surface area of the fuel zone;    -   the exhaust zone has at least two exhaust outlets, wherein the        total surface area of these exhaust outlets is 20% to 35% of the        total surface area of the exhaust zone; and    -   the combustion zone has at least three air inlets, wherein the        total surface area of these air inlets is 2.5% to 4.0% of the        total surface area of the combustion zone.

As noted above, methyl, ethyl, propyl, and butyl esters of C6-C14carboxylic acids, which shall be referred to as fatty acid esters (FAE),are particularly advantageous as the fuel of solid fuel blocks. Of thesemethyl decanoate is currently the most popular. The present inventionconcerns stoves which are specifically designed to efficiently burnthese FAE solid fuel blocks.

In the past, cooking stoves that burn wood, charcoal briquettes, driedpeat, coal, etc., have relied on having air inlets at fuel height todirectly feed the burning fuel with air. A new way of burning adapted toFAE solid fuel blocks has been discovered by the inventor. If air isrestricted from accessing the burning fuel at fuel height but issupplied to a headspace above the burning fuel, the main combustionoccurs in this headspace above fuel height. The inventor has found thatthis leads to more efficient combustion than burning only the fuel blockitself. This has led to the stove of the present invention, which hasbeen designed to control the air flow in order to most efficientlycombust FAE solid fuel blocks, resulting in more efficient transfer ofenergy from the fuel to a cooking vessel placed on the stove, and areduction in the soot and unburned volatile organic compounds that arepresent in the exhaust fumes that can be deposited on the cookingvessel.

Lightweight portable cooking stoves which are designed to improve theefficiency with which solid fuel blocks can be burned have beendescribed in the presently unpublished patent application numberPCT/GB2013/000176. This patent application describes a cooking stovecomprising sheet-like members which are coupled together at their sideedges, with at least one exhaust opening at or close to the top edge,and with a lattice of perforations which acts as air inlets and whichcovers at least 60% of the surface area of the faces of the sheet-likemember. Using a lattice of perforations to let air into the stove wasfound to restrict airflow into the stove in a manner that reduces theintensity with which a solid fuel block burns, so that more efficientcombustion can take place. However, further investigations have revealedthat soot deposition is still a problem. Soot deposition reveals thatpartial combustion has taken place.

As mentioned above, the cooking stove of the present invention isdesigned specifically to tightly control the air flow into and exhaustgas flow out of the cooking stove to ensure that it is optimal forcombustion of a FAE solid fuel block.

To this end, a fuel zone is provided at the lowest third of the stove,which advantageously is approximately the same height a fuel blockitself, or can be taller than a fuel block. In the fuel zone relativelysmall and/or few air inlets (just 0.5% to 2.5% of the total surface areain this zone) are provided to allow air to be drawn in to sustain just asmall flame which, alone, would burn the fuel at a slow rate. The mainpurpose of the flame in the fuel zone is to create enough heat tovaporise the FAE so that complete combustion can take place in theheadspace above the fuel, in the combustion zone. This is in starkcontrast to many prior art stoves, where the biggest, and often theonly, air inlets are at the level of the fuel. With traditional fuelsthat are not subject to vaporisation (wood, coal etc.) completecombustion has to take place at the level of the fuel itself. As notedabove, the stove of the present invention has been carefully designed tofully optimise and control burning of FAE solid fuel blocks.

The combustion zone has been designed to take up the middle third of thecooking stove, and is typically above a fuel block when positioned inthe stove. In order to facilitate complete combustion of the solid fuelblock, larger and/or a greater number of air inlets are provided in thecombustion zone compared to the fuel zone. At least three air inlets areprovided in the combustion zone. These make up 2.5% to 4.0% of thesurface area of this zone, so the total surface area of the air inletsin the combustion zone is generally greater than the total surface areaof the air inlet or air inlets in the fuel zone. This helps to ensurethat the flame is hot enough in the combustion zone to completelycombust the fuel, compared to in prior art stoves where incompletecombustion can mean that partially combusted fuel, i.e. soot or, worsestill, vaporised but completely unburned fuel, is deposited on thecooking vessel.

Controlling the flow of gasses out of the stove is also important. Tothis end, an exhaust zone is provided in the top third of the stove thathas at least two exhaust outlets, with a total surface area of 20% to35% of the total surface area of the exhaust zone. In particular, thefact that the air inlets in both the fuel zone and the combustion zoneare severely restricted, and surface area of the air inlets in thecombustion zone are equal to or greater than that of the air inlets inthe fuel zone, is key to the improved performance.

The specific arrangement of air inlets and exhaust outlets in the threezones of the stove of the present invention advantageously allows theflow of gasses into and out of the stove to be tightly controlled inorder to promote complete combustion of a FAE fuel block in anon-aggressive manner which can advantageously result in a clean blueflame and a good balance between burn time and flame temperature foroptimal heating of food or liquid in a cooking vessel on the stove.Prior art stoves generally have the largest or indeed the only airinlets in the fuel zone. The unpublished patent application numberPCT/GB2013/000176 discloses a stove which is designed to burn solid fuelblocks. This has a lattice of perforations forming the air inlets andoutlets. The surface area of the perforations in the fuel zone arelarger than in combustion zone (8 to 9% compared to 7 to 8%) and areboth considerably larger than in the present invention. The exhaustoutlets are considerably smaller than in the present invention (around10%). Restricting the air inlets, as in the present invention leads tobetter performance, and significantly, to much lower soot deposition.

According to a second aspect, the present invention relates to a kitcomprising a cooking stove according to the first aspect of theinvention, and one or more solid fuel blocks, wherein the one or moresolid fuel blocks comprise methyl, ethyl, propyl, or butyl esters of aC6 to C14 carboxylic acid or mixtures thereof. As set out above, thesolid fuel block preferably comprises methyl decanoate.

According to a third aspect, the present invention relates to a methodof heating a cooking vessel, the method comprising the steps of:

-   -   providing a cooking stove according to the first aspect of the        invention;    -   providing a solid fuel block, wherein the solid fuel block        comprises methyl, ethyl, propyl, or butyl ester of a C6 to C14        carboxylic acid or mixtures thereof;    -   placing the solid fuel block in the fuel zone of the cooking        stove and setting light to the solid fuel block; and    -   placing the cooking vessel on top of the cooking stove.

According to a fourth aspect, the present invention relates to a cookingstove substantially as described herein, and/or as shown in theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 relates to a four sided cooking stove according to a preferredembodiment of the present invention.

FIG. 2 relates to the four sided cooking stove as shown in FIG. 1, whichhas been disassembled.

FIG. 3 relates to a four sided cooking stove according to a furtherpreferred embodiment of the present invention.

FIG. 4 relates to the four sided cooking stove as shown in FIG. 3, whichhas been disassembled.

DESCRIPTION

The present invention relates to a cooking stove. As set out above, thecooking stoves of the present invention are designed to make efficientuse of solid fuel blocks and to minimise the soot deposited on thecooking vessel. The cooking stove has walls which define a base at oneend and a top at the other end. By walls, we mean a continuous loop ofmaterial that is open at both ends. One open end, designated the “base”,is positioned lowermost, and placed on a solid surface during use. Theopposing open end, designated the “top”, is positioned uppermost duringuse, and provides a cooking surface upon which cooking vessels can beplaced.

By “height” of the stove, we mean the dimension from the top to thebase. The “width” is at 90 degrees to this, taking the widestcross-section through the stove, for example at the top or the base.

In the stove of the present invention, the height is preferably greaterthan the width of the stove at the widest point. For example, the heightof the stove can be at least 20% greater than the width of the stove atthe widest point. This can help to ensure that there is enough headspacein the combustion zone to efficiently and completely combust all thevolatized fuel. In other embodiments, the height and width of the stoveare approximately equal, or the stove can be up to 20% wider than it ishigh.

The walls of the cooking stove can be cylindrical or conical, or cancomprise 3, 4, 5 or 6 sides wherein each side defines a substantiallysquare, rectangular or trapezium shape so that the cooking stove definesa substantially cuboid, prism or pyramidal frustum shape.

Where the cooking stove has walls which comprise 3, 4, 5 or 6 sides, thesides can be described as “sheet-like members”. By sheet-like member wemean a sheet of material that can be either planar or curved, and is ofa shape that can be defined as having a top edge, a bottom edge, twoside edges and two faces. Typically this would be achieved by thesheet-like member having a substantially square, rectangular ortrapezium shape when viewed face-on. When a rectangular sheet-likemember is used, either the long edge or the short edge would define thebottom edge. When a trapezium-shaped sheet-like member, either of theparallel edges would define the bottom edge. It is intended that, duringuse, the bottom edge will be lowermost, typically on the ground, orother support, and i.e. would form the base, and the top edge will beuppermost i.e. would form the top.

The sheet-like members can be coupled together at their side edges toform the walls of the cooking stove. By coupled at their side edges, wemean that the side edges must be aligned such that the length of theside edge of one sheet-like member is substantially positioned along thelength of the side edge of the other sheet-like member. The side edges,therefore, include a coupling mechanism that holds the two side edgestogether.

The coupling mechanism can be the shape of the side edge, or the regionclose to the side edge, or can be a hinge. The coupling mechanism ispreferably such that no gaps are created which could act as air inletsor exhaust outlets.

In a preferred embodiment of the present invention, the couplingmechanism is reversible, so that the sheet-like members can be readilydisassembled. By this we mean that after use, at least one of thecouplings between sheet-like members can be separated. The sheet-likemembers can then be stored in a flat-packed configuration. Byflat-packed configuration, we mean that the sheet-like members can bearranged such that they are stacked with their faces aligned, thustaking up minimal space. This makes the cooking stove more easilyportable, which is highly advantageous.

The sheet-like members may, for example, be coupled using a slitsubstantially parallel to and within 50 mm of the side edges. By this,we mean that a substantially rectangular section, with two long edgesand two short edges, is missing from the sheet-like member, the longedges of the slit running substantially parallel to the side edge, andthe short edges defining a width that is at least that of the thicknessof the sheet-like member. The slit may also be cut into a protrudingsection of the side edge. The slit may extend from either the top or thebottom edge, or the top or the bottom edge of a protruding section ofthe side edge, such that three edges of the slit are defined by thesheet-like member and the final edge is a short edge that is open. Theslit may also be positioned such that the slit is closed on all fouredges. The slit of one sheet-like member can couple with a complementaryslit of another sheet-like member. By complementary, we mean that whereone slit has an open edge facing the bottom edge of the sheet-likemember, the other slit has an open edge facing the top edge of thesheet-like member, and the slits are both positioned such that they canbe used to couple the members. Where a first slit is closed on all fouredges, the complementary second slit is a slit with an open narrow edgefacing either the top or bottom edge of the sheet-like member, andhaving a closed narrow edge at substantially the same height as eitherthe upper or lower closed narrow edge of the first slit. Twocomplementary edges can be coupled by inserting the complementary slitsinto each other.

A further option is that the sheet-like members can be coupled usinghinges. By this we mean that the mechanism that holds the two side edgestogether is a pivoting hinge that pivots along the same axis as the sideedge. Using this mechanism, the sheet-like members can be folded intothe stove configuration for use, and after use can be folded into aflat-pack configuration for storage. The hinges are preferably halfhinges, that extend from the bottom of the sheet like members to thetop, so that no gap is left which could act as an air inlet or exhaustoutlet. In a preferred embodiment, all apart from one of the hingescannot be disassembled by the user. One can be disassembled/assembled bythe user. When it is disassembled, the sheet-like members can becollapsed on top of one another in a concertinaed arrangement, so as tobe flat-packed. To be assembled, they are arranged to stand in acircuit, and the one hinge is assembled by the user to complete thestove.

The stove comprises at least three sheet-like members, and preferablycomprises four to six sheet-like members, more preferably foursheet-like members. Using three sheet-like members as an example, afirst side-edge of a first sheet-like member is coupled to a firstside-edge of a second sheet-like member. The second side-edge of thesecond sheet-like member is coupled to a first-side edge of a thirdsheet-like member. The second side-edge of the third sheet-like memberis coupled to the second side-edge of the first sheet-like member, thuscreating a closed loop of sheet-like members. To create a stove withmore sheet-like members, the same principle is applied to create a loopof sheet-like members, coupled at their side-edges.

Where a sheet-like member has a square or rectangular shape, theassembled stove will resemble a prism. Where three sheet-like membersare used, the assembled stove will resemble a triangular-based prism.Where four sheet-like members are used, the assembled stove willresemble a square-based prism, or a cuboid. Where five sheet-likemembers are used, the assembled stove will resemble a pentagon-basedprism. Where six sheet-like members are used, the assembled stove willresemble a hexagonal-based prism, and so on.

Where a sheet like-member has a trapezium-shaped sheet-like member, andthe long parallel edge defines the bottom edge, the assembled stove willresemble a pyramidal frustum. Where a sheet-like member has atrapezium-shaped sheet-like member, and the short parallel edge definesthe bottom edge, the assembled stove will resemble an inverted pyramidalfrustum. Where three sheet-like members are used, the assembled stovewill resemble a triangular-based pyramidal frustum. Where foursheet-like members are used, the assembled stove will resemble asquare-based pyramidal frustum. Where five sheet-like members are used,the assembled stove will resemble a pentagon-based pyramidal frustum.Where six sheet-like members are used, the assembled stove will resemblea hexagon-based pyramidal frustum, and so on.

In the cooking stove of the present invention, the walls of the cookingstove define a fuel zone, a combustion zone and an exhaust zone. Byreferring to the difference zones, we are imagining that the stove isdivided into three sections of equal height, based on the way the stoveis used. There is no physical barrier or transition between thedifferent zones. The fuel zone is defined by the section of the wallswhich extends up from the base to about one third of the height of thestove. The exhaust zone is defined by the section of the walls whichextends down from the top by about one third of the height of the stove.The combustion zone is defined by the section of the walls which extendsfrom the fuel zone to the exhaust zone, so occupies the middle third ofthe stove.

As set out above, the height of the stove is the dimension from top tobase. Accordingly, the fuel zone is provided at the lowest third of thestove, which advantageously is approximately the same height a fuelblock itself, or can be taller than a fuel block. The fuel zone has atleast one air inlet, wherein the total surface area of this air inlet orair inlets is 0.5% to 2.5% of the total surface area of the fuel zone.The inventor has discovered that the air inlets in the fuel zone have animportant effect on the cleanness of the flame and efficiency with whichthe fuel is burnt. When the air inlets(s) in the fuel zone comprise lessthan 0.5% of the total surface area of the fuel zone, it is believedthat not enough air can enter to sustain flame. Above 2.5% of the totalsurface area of the fuel zone, the blue clean burn flame can be changeinto a yellow flame, and sooty deposits may appear on the cookingvessel.

Air inlets and exhaust outlets are essentially holes in the walls of thecooking stove. When we refer to the surface area of air inlets orexhaust outlets as a percentage of the total surface area of a zone, wemean the total surface area of the walls that is missing in that zone asa percentage of the total surface area of the walls of the zone, ifthere was no material missing.

Compared to traditional stoves, the fuel zone in a stove of the presentinvention has a relatively small proportion of air inlet surface areaand typically allows air to be drawn in to sustain just a small flamewhich, alone, would burn the fuel at a slow rate. The main purpose ofthe flame in the fuel zone is to create enough heat to vaporise the FAEso that complete combustion can take place in the headspace above thefuel, in the combustion zone.

The air inlet or at least one of the air inlets in the fuel zonepreferably has a diameter of at least 8 mm, preferably about 10 mm. Thisis convenient because it allows a match or other igniter to be passedthrough the air inlet to light the fuel.

The combustion zone has been designed to take up the middle third of thecooking stove, and is typically above a fuel block when positioned inthe stove. In order to facilitate complete combustion of the solid fuelblock, larger and/or a greater number of air inlets are provided in thecombustion zone compared to the fuel zone. At least three air inlets areprovided in the combustion zone. The total surface area of these airinlets is 2.5% to 4.0% of the total surface area of the combustion zone.This is in stark contrast to many prior art stoves, where the biggest,and often the only, air inlets are at the level of the fuel.

With traditional fuels that are not subject to vaporisation (wood, coaletc.) complete combustion has to take place at the level of the fuelitself. As noted above, the stove of the present invention has beencarefully designed to fully optimise and control burning of FAE solidfuel blocks. Having relatively large air inlets in the combustion zonehelps to ensure that the flame is hot enough in the combustion zone tocompletely combust the fuel, compared to in prior art stoves whereincomplete combustion can mean that partially combusted fuel, i.e. sootor, worse still, vaporised but completely unburned fuel is deposited onthe cooking vessel.

The inventor has found that by altering the surface area of the airinlets in the combustion zone, the rate of burn of a solid fuel blockcan be tuned. At below 2.5%, the burn is too slow to be of optimal use.Between 2.5% and 4%, the burn is of an acceptable time and optimalintensity to result in complete combustion with a clean blue flamegiving no or almost no sooty deposits, with 2.5% giving a slower andsteadier burn than 4%. Above 4%, a solid fuel block can burn tooaggressively to completely combust, resulting in sooty deposits on thebottom of the cooking vessel.

Controlling the flow of gasses out of the stove is also important. Tothis end, an exhaust zone is provided in the top third of the stove thathas at least two exhaust outlets. The total surface area of theseexhaust outlets is optimally 20% to 35% of the total surface area of theexhaust zone.

During use, a cooking vessel is placed over the top of the walls of thestove, preferably so that it completely covers the top of the stove. Inthis way, the exhaust outlets are the only gaps between the cookingstove and the cooking vessel through which hot exhaust gasses canescape.

The specific arrangement of air inlets and exhaust outlets in the threezones of the stove of the present invention advantageously allows theflow of gasses into and out of the stove to be tightly controlled inorder to promote complete combustion of a FAE fuel block in anon-aggressive manner which can advantageously result in a clean blueflame and a good balance between burn time and flame temperature foroptimal heating of food or liquid in a cooking vessel on the stove.

The inventor has, surprisingly, found that the total surface area of theinlets/outlets in the particular zones is more important to theperformance than the specific arrangement of inlets/outlets.Accordingly, any reasonable number and arrangement of inlets/outlets canbe used, providing the number of and total surface area of theinlets/outlets falls within the claimed ranges. Specific examples aredescribed below, and shown in the accompanying figures. It is preferredthat there are 1 to 12 air inlets in the fuel zone, and/or 4 to 20 airinlets in the combustion zone, and/or 2 to 6 exhaust outlets in theexhaust zone.

In one embodiment of the present invention, the cooking stove has wallswhich comprise four sides, with one air inlet in the fuel zone, twelveair inlets in the combustion zone, and two exhaust outlets in theexhaust zone. In this embodiment, it is preferably that the air inlet inthe fuel zone comprises about 1% of the total surface area of the fuelzone, the air inlets in the combustion zone comprise about 3.5% of thetotal surface area of the combustion zone, and the exhaust outletscomprise about 23% of the total surface area of the exhaust zone.

In another preferred embodiment of the present invention, the walls ofthe stove comprise four sides, with eight air inlets in the fuel zone,sixteen air inlets in the combustion zone, and four exhaust outlets inthe exhaust zone. In this embodiment, it is preferred that the airinlets in the fuel zone comprise about 2.1% of the total surface area ofthe fuel zone, the air inlets in the combustion zone comprise about 3.5%of the total surface area of the combustion zone, and the exhaustoutlets comprise about 23% of the total surface area of the exhaustzone.

As set out above, the cooking stoves of the present invention can beused by those undertaking general camping, military or other outdoorleisure pursuits, or by larger groups of people for entertaining orhumanitarian purposes.

For camping and military uses, the stove is usually designed to heataround 500 ml of water or food. Such a stove is typically 5 cm to 10 cmhigh, preferably about 8 cm high and 5 to 10 cm wide at the widestpoint, typically around 8 cm wide at the widest point.

For humanitarian or family use, the stove is usually designed to heataround 51 of water or food. Such a stove is typically 10 cm to 20 cmhigh, preferably about 12 cm high and 10 to 20 cm wide at the widestpoint, typically around 14 cm wide at the widest point. A stove forhumanitarian use advantageously has slotted rather than hinged sides toprovide a stable base for a relatively large cooking vessel.

As noted above, the stove of the present invention is designedspecifically for use with a FAE solid fuel block. FAE solid fuel blockstypically comprise a methyl, ethyl, propyl or butyl ester of a C6 to C14carboxylic acid or combination thereof encapsulated in a solid emulsion.A solid fuel block comprising an emulsion of methyl decanoateencapsulated in a urea-formaldehyde resin is available on the marketunder the name “Zip Military Fuel”® These fuel blocks comprise about 20%by weight urea-formaldehyde/water/emulsifier matrix and about 80% byweight methyl decanoate. Two sizes are available, a 26 g block that is42 mm long, 32 mm wide and 20 mm tall, and a 100 g block that is 60 mmlong, 60 mm wide and 40 mm tall. The smaller block is usually forindividual use, for example by campers or the military, and the largerblock can be for humanitarian use.

Accordingly, the present invention also relates to a kit comprising acooking stove and one or more such solid fuel blocks. The presentinvention also relates to a method of heating a cooking vessel using oneof the solid fuel blocks. The relative dimensions of the solid fuelblock and the stove should be such that the solid fuel block isdimensioned to fit inside the lowest third of the cooking stove i.e. thefuel zone. Accordingly, in one embodiment of the invention, the heightof the fuel zone is equal to or greater than the height of the fuelblock.

The cooking stove of the present invention is constructed from afire-proof material, preferably wherein the material is a metal or alloysuch as aluminium, titanium, nickel, copper, mild steel, stainless steelor brass. This ensures that the stove is able to withstand the heat ofthe burning fuel without burning or substantially deforming while beingstrong enough to support a cooking vessel and robust enough for repeateduse.

DETAILED DESCRIPTION OF THE DRAWINGS

In one preferred embodiment, as shown in FIGS. 1 and 2, a cooking stove1 has four sides, 2, 3, 4, 5. Preferably the sides are hinged together6, 7, 8, with one of the hinges, 9, being suitable for disassembly bythe user, to allow the stove to be flat packed. In FIG. 2, it is showndisassembled. The sides can be concertinaed to flat pack, not shown.

There is one air inlet 10 in the fuel zone 14, twelve air inlets 11 inthe combustion zone 15, three on each side, and two exhaust outlets 12in the exhaust zone 16. The air inlet 10 in the fuel zone 14 is a single10 mm diameter hole, which comprises around 1% of the total surface areaof the fuel zone. The air inlets 11 in the combustion zone 15 are eachabout 5 mm in diameter, which together make up about 3.5% of the totalsurface area of the combustion zone. The exhaust outlets 12 arescalloped and are positioned on opposing sides from each other. Theexhaust outlets are not on the same side as the air inlet in the fuelzone. The exhaust outlets 12 make up about 23% of the total surface areaof the exhaust zone 16.

This stove is particularly well suited to use on a small scale, for anindividual or a couple, to boil a small amount, about 250-500 ml ofwater or food. It can be used with a small fuel block i.e. a 26 g blockthat is 42 mm long, 32 mm wide and 20 mm tall. The base of the stove 12is placed on a level surface. A fuel block (not shown) is placed on thesurface inside the stove. The fuel block is set alight by passing amatch or other igniter through air inlet 10 in the fuel zone 14.

As described above, a restricted volume of air is drawn in through theinlet 10, to give rise to a small flame, which burns the fuel block witha small flame in the fuel zone 14, and which vaporises fuel which risesto the combustion zone 15. A higher volume of air can be drawn throughthe air inlets 11 in the combustion zone 15 where the majority ofcombustion takes place.

A cooking vessel (not shown) is placed over the entirety of the top 17of the stove which forces the exhaust gasses out of the exhaust outlets12. The flame produced is blue, showing that complete combustion hasoccurred, and soot or FAE deposits on the cooking vessel are minimal.

In a further preferred embodiment, as shown in FIGS. 3 and 4, a cookingstove 20 has four sides, 21, 22, 23 and 24. The sides are slottedtogether using slots 25, 26, 27 and 28 as shown disassembled in FIG. 4.This allows the stove to be flat packed.

There are eight air inlets 29 in the fuel zone 30, sixteen air inlets 33in the combustion zone 31, four on each side, and four exhaust outlets34 in the exhaust zone 32. The exhaust outlets 34 are shaped to allowedefficient burning, and are positioned with one on each of the foursides. The air inlets in the fuel zone comprise about 2.1%, in thecombustion zone about 2.9% and exhaust outlets in the exhaust zone about30% of the total surface area of each zone respectively.

This stove is particularly well suited to use on a humanitarian scale,for a whole family or group of families, up to 50 people. It wouldusually be used to boil a large amount, about 51 of water or food. Itcan be used with one or more large fuel blocks i.e. a 100 g block thatis 60 mm long, 60 mm wide and 40 mm tall.

The base of the stove 35 is placed on a level surface. A fuel block (notshown) is placed on the surface inside the stove. The fuel block is setalight by passing a match or other igniter through one of the air inlets29 in the fuel zone 30.

As described above, a restricted volume of air is drawn in through theinlets 29, to give rise to a small flame, which burns the fuel blockwith a small flame in the fuel zone 30, and which vaporises fuel whichrises to the combustion zone 31. A higher volume of air can be drawnthrough the air inlets 33 in the combustion zone 31 where the majorityof combustion takes place. A cooking vessel (not shown) is placed overthe entirety of the top 36 of the stove 20 which forces the exhaustgasses out of the exhaust outlets 34. The flame produced is blue,showing that complete combustion has occurred, and soot or FAE depositson the cooking vessel are minimal.

1. A cooking stove, the cooking stove comprising walls which define abase at one end and a top at the other end, wherein the walls of thecooking stove additionally define: a fuel zone which is defined by thesection of the walls which extends up from the base to about one thirdof the height of the stove; an exhaust zone which is defined by thesection of the walls which extends down from the top by about one thirdof the height of the stove; and a combustion zone which is defined bythe section of the walls which extends from the fuel zone to the exhaustzone; wherein the cooking stove is characterised in that the fuel zonehas at least one air inlet, wherein the total surface area of this airinlet or air inlets is 0.5% to 2.5% of the total surface area of thefuel zone; the exhaust zone has at least two exhaust outlets, whereinthe total surface area of these exhaust outlets is 20% to 35% of thetotal surface area of the exhaust zone; and the combustion zone has atleast three air inlets, wherein the total surface area of these airinlets is 2.5% to 4.0% of the total surface area of the combustion zone.2. The cooking stove according to claim 1, wherein the walls arecylindrical, conical, or wherein the walls comprise 3, 4, 5 or 6 sideswherein each side defines a substantially square, rectangular ortrapezium shape so that the cooking stove defines a substantiallycuboid, prism or pyramidal frustum shape.
 3. The cooking stove accordingto claim 1, wherein the walls comprise 3, 4, 5 or 6 sides which aresheet-like members, wherein each sheet-like member has two faces, a topedge, a bottom edge and two side edges, and wherein the sheet-likemembers are coupled together at their side edges.
 4. The cooking stoveaccording to claim 3, wherein the walls comprise 4 sides which aresheet-like members.
 5. The cooking stove according to claim 3, whereinthe coupling between the side edges of sheet-like members is not fixed,so the cooking stove can be assembled and disassembled during normaluse, preferably wherein when the cooking stove is disassembled, thesheet-like members can be arranged to lie flat on top of one another. 6.The cooking stove according to claim 5, wherein the sheet-like membersare coupled by hinges.
 7. The cooking stove according to claim 5,wherein the sheet-like members have a slit substantially parallel to andwithin 50 mm of the side edges, wherein the sheet-like members arecoupled at their side edges through the interlocking of complementaryslits.
 8. The cooking stove according to claim 1, wherein the height ofthe stove is greater than the width of the stove at the widest point. 9.The cooking stove according to claim 8, wherein the height of the stoveis at least 20% greater than the width of the stove at the widest point.10. The cooking stove according to claim 1, wherein the walls comprisefour sides, and wherein there is one air inlet in the fuel zone, twelveair inlets in the combustion zone, and two exhaust outlets in theexhaust zone.
 11. The cooking stove according to claim 10, wherein theair inlet in the fuel zone comprises about 1% of the total surface areaof the fuel zone, the air inlets in the combustion zone comprise about3.5% of the total surface area of the combustion zone, and the exhaustoutlets comprise about 23% of the total surface area of the exhaustzone.
 12. The cooking stove according to claim 1, wherein the wallscomprise four sides, and wherein there are eight air inlets in the fuelzone, sixteen air inlets in the combustion zone, and four exhaustoutlets in the exhaust zone.
 13. The cooking stove according to claim12, wherein the air inlets in the fuel zone comprise about 2.1% of thetotal surface area of the fuel zone, the air inlets in the combustionzone comprise about 3.5% of the total surface area of the combustionzone, and the exhaust outlets comprise about 23% of the total surfacearea of the exhaust zone.
 14. The cooking stove according to claim 1,wherein the air inlet or at least one of the air inlets in the fuel zonehas a diameter of at least 8 mm, preferably about 10 mm.
 15. A kitcomprising a cooking stove according to claim 1, and one or more solidfuel blocks, wherein the one or more solid fuel blocks comprise methyl,ethyl, propyl, or butyl esters of a C6 to C14 carboxylic acid ormixtures thereof.
 16. A kit according to claim 15, wherein the solidfuel block comprises methyl decanoate.
 17. A kit according to claim 15,wherein the solid fuel block fits inside the fuel zone of the cookingstove.
 18. A method of heating a cooking vessel, the method comprisingthe steps of: providing a cooking stove according to claim 1; providinga solid fuel block, wherein the solid fuel block comprises methyl,ethyl, propyl, or butyl esters of a C6 to C14 carboxylic acid ormixtures thereof; placing the solid fuel block in the fuel zone of thecooking stove and setting light to the solid fuel block; and placing thecooking vessel on top of the cooking stove.
 19. A method according toclaim 18, wherein the solid fuel block comprises methyl decanoate.
 20. Amethod according to claim 18 or 19, wherein the height of the fuel zoneis equal to or greater than the height of the fuel block.
 21. (canceled)